Validation options

opt1.rb

#this option is more explicit, but not as DRY and flexible
module BaseValidator
  def validate_each(rec, attr, val)
    #calls one or two known methods
  end
end

class AsFooValidator < ActiveModel::EachValidator
  include BaseValidator
  def foo #one of the known methods
  end
end

class Foo < ActiveRecord::Base
  validates :foo, :as_foo => { :more_options => here }
end

opt2.rb

#this option is more "magical", but it is DRY, and could be more flexible using callbacks 
module ValidatorCreator
  def self.included(obj)
    cls_name = obj.name + "Validator"
    newobj = Object.const_set cls_name, Class.new(ActiveModel::EachValidator)
    newobj.send(:include, obj)
  end

  def validate_each(rec, attr, val)
    #calls one or two known methods
  end
end

module AsFoo
  include ValidatorCreator #generates AsFooValidator
  def foo #known method
  end
end

class Foo < ActiveRecord::Base
  validates :foo, :as_foo => { :more_options => here }
end